Substrate processing method and substrate processing apparatus

ABSTRACT

A substrate processing method includes placing a substrate with a dielectric film on a substrate support in a chamber, and etching the dielectric film with plasm generated from a reaction gas containing an HF gas and at least one CxHyFz gas selected from the group consisting of a C4H2F6 gas, a C4H2F8 gas, a C3H2F4 gas, and a C3H2F6 gas. The etching includes setting the substrate support at a temperature of 0° C. or lower and setting the HF gas to a flow rate greater than a flow rate of the CxHyFz gas.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a bypass continuation-in-part application of international application No. PCT/JP2021/017473 having an international filing date of May 7, 2021, the entire contents of which are incorporated herein by reference. This application is also related to U.S. Ser. No. 17/666,570, entitled: ETCHING METHOD, filed on Feb. 8, 2022 and U.S. Ser. No. 17/092,376, entitled: SUBSTRATE PROCESSING METHOD AND SUBSTRATE PROCESSING APPARATUS, filed on Nov. 9, 2020, the entire contents of which are incorporated herein by reference.

FIELD

Exemplary embodiments of the present disclosure relate to a substrate processing method and a substrate processing apparatus.

BACKGROUND

For example, Patent Literature 1 describes a technique for etching a silicon oxide film.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2016-122774

BRIEF SUMMARY Technical Problem

One or more aspects of the present disclosure are directed to a technique for improving the selectivity of a dielectric film to a mask in etching.

Solution to Problem

A substrate processing method according to one exemplary embodiment includes placing a substrate with a dielectric film on a substrate support in a chamber, and etching the dielectric film with plasm generated from a reaction gas containing an HF gas and at least one C_(x)H_(y)F_(z) gas selected from the group consisting of a C₄H₂F₆ gas, a C₄H₂F₈ gas, a C₃H₂F₄ gas, and a C₃H₂F₆ gas. The etching includes setting the substrate support at a temperature of 0° C. or lower and setting the HF gas to a flow rate greater than a flow rate of the C_(x)H_(y)F_(z) gas.

Advantageous Effects

The technique according to one exemplary embodiment of the present disclosure improves the selectivity of a dielectric film to a mask in etching.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a substrate processing apparatus 1.

FIG. 2 is a timing chart showing example radio-frequency (RF) power HF and an example electrical bias.

FIG. 3 is a schematic diagram of a substrate processing system PS.

FIG. 4 is a diagram of a substrate W showing an example cross-sectional structure.

FIG. 5 is a flowchart of a processing method.

FIG. 6 is a diagram of example features of mask films MK after etching.

FIG. 7 is a graph showing an example of temperature dependence of etching.

FIG. 8 is a diagram of the substrate W in step ST22 showing an example cross-sectional structure.

FIG. 9 is a graph showing the measurement results of Experiment 1.

FIG. 10 is a graph showing the measurement results of Experiment 2.

FIG. 11 is a graph showing the measurement results of Experiment 2.

FIG. 12 is a graph showing the measurement results of Experiment 3.

FIG. 13 is a graph showing the measurement results of Experiment 3.

FIG. 14 is a graph showing the measurement results of Experiment 4.

DETAILED DESCRIPTION

One or more embodiments of the present disclosure will be described below.

A substrate processing method according to one exemplary embodiment includes placing a substrate with a dielectric film on a substrate support in a chamber, and etching the dielectric film with plasm generated from a reaction gas containing an HF gas and at least one C_(x)H_(y)F_(z) gas selected from the group consisting of a C₄H₂F₆ gas, a C₄H₂F₈ gas, a C₃H₂F₄ gas, and a C₃H₂F₆ gas. The etching includes setting the substrate support at a temperature of 0° C. or lower and setting the HF gas to a flow rate greater than a flow rate of the C_(x)H_(y)F_(z) gas.

In one exemplary embodiment, the flow rate of the C_(x)H_(y)F_(z) gas is less than or equal to 20% by volume of a total flow rate of the reaction gas.

In one exemplary embodiment, the flow rate of the HF gas is greater than or equal to 70% by volume of a total flow rate of the reaction gas.

In one exemplary embodiment, the reaction gas further contains a halogen-containing gas.

In one exemplary embodiment, the halogen-containing gas is at least one selected from the group consisting of a chlorine-containing gas, a bromine-containing gas, and an iodine-containing gas.

In one exemplary embodiment, the halogen-containing gas is at least one gas selected from the group consisting of Cl₂, SiCl₂, SiCl₄, CCl₄, SiH₂Cl₂, Si₂Cl₆, CHCl₃, SO₂Cl₂, BCl₃, PCl₃, PCl₅, POCl₃, Br₂, HBr, CBr₂F₂, C₂F₅Br, PBr₃, PBr₅, POBr₃, BBr₃, HI, CF₃I, C₂F₅I, C₃F₇I, IF₅, IF₇, I₂, and PI₃.

In one exemplary embodiment, the reaction gas contains a phosphorus-containing gas.

In one exemplary embodiment, the reaction gas contains an oxygen-containing gas.

In one exemplary embodiment, the reaction gas further contains at least one selected from the group consisting of a boron-containing gas and a sulfur-containing gas.

In one exemplary embodiment, the plasma is generated from a process gas containing the reaction gas and an inert gas.

In one exemplary embodiment, the dielectric film is a silicon-containing film.

In one exemplary embodiment, the silicon-containing film includes at least one selected from the group consisting of a silicon oxide film, a silicon nitride film, and a polysilicon film.

In one exemplary embodiment, the substrate includes a mask including an organic film defining at least one opening on the dielectric film or a metal-containing film defining at least one opening on the dielectric film.

In one exemplary embodiment, the etching includes applying an electrical bias to the substrate support. A period during which the electrical bias is applied to the substrate support includes a first period and a second period alternating with the first period. The electrical bias in the first period is zero or at a first level, and the electrical bias in the second period is at a second level higher than the first level.

In one exemplary embodiment, the etching includes providing radio-frequency power for generating plasma to the substrate support or to an upper electrode facing the substrate support. A period during which the radio-frequency power is provided includes a third period and a fourth period alternating with the third period. The radio-frequency power in the third period is zero or at a third level, and the radio-frequency power in the fourth period is at a fourth level higher than the third level. The second period and the fourth period at least partially overlap.

In one exemplary embodiment, the electrical bias is a pulsed voltage.

In one exemplary embodiment, the etching includes providing a direct-current voltage or low-frequency power to an upper electrode facing the substrate support.

In one exemplary embodiment, the etching includes a first process of setting the chamber to a first pressure, applying a first electrical bias to the substrate support, and etching the dielectric film, and a second process of setting the chamber to a second pressure, applying a second electrical bias to the substrate support, and etching the dielectric film. The first pressure differs from the second pressure or the first electrical bias differs from the second electrical bias, or the first pressure differs from the second pressure and the first electrical bias differs from the second electrical bias.

In one exemplary embodiment, the first pressure is higher than the second pressure.

In one exemplary embodiment, an absolute value of the first electrical bias is greater than an absolute value of the second electrical bias.

In one exemplary embodiment, the first process and the second process are repeated alternately.

A substrate processing method according to one exemplary embodiment includes placing a substrate with a silicon-containing film including a silicon oxide film on a substrate support in a chamber, and etching the silicon-containing film with plasm generated from a reaction gas containing a fluorine-containing gas and a C_(x)H_(y)F_(z) gas being a gas different from the fluorine-containing gas, where x is an integer greater than or equal to 2, and y and z are integers greater than or equal to 1. The etching includes setting the substrate support at a temperature of 0° C. or lower and setting the C_(x)H_(y)F_(z) gas to a flow rate less than or equal to 20% by volume of a total flow rate of the reaction gas.

In one exemplary embodiment, the fluorine-containing gas is a gas to produce an HF species in the chamber.

In one exemplary embodiment, the C_(x)H_(y)F_(z) gas includes one or more CF₃ groups.

In one exemplary embodiment, the C_(x)H_(y)F_(z) gas contains at least one selected from the group consisting of a C₃H₂F₄ gas, a C₃H₂F₆ gas, a C₄H₂F₆ gas, a C₄H₂F₈ gas, and a C₅H₂F₆ gas.

In one exemplary embodiment, a flow rate of the fluorine-containing gas is highest in the reaction gas.

A substrate processing method according to one exemplary embodiment includes placing a substrate with a silicon-containing film including a silicon oxide film on a substrate support in a chamber, generating plasma in the chamber, and etching the silicon-containing film using an HF species and a C_(x)H_(y)F_(z) species in the plasma, where x is an integer greater than or equal to 2, and y and z are integers greater than or equal to 1. The plasma includes a greatest amount of the HF species.

A substrate processing apparatus according to one exemplary embodiment includes a chamber, a substrate support in the chamber and adjustable in temperature, a plasma generator that provides electric power to generate plasma in the chamber, and a controller. The controller performs a control operation including introducing, using the electric power provided from the plasm generator, a reaction gas containing an HF gas and at least one C_(x)H_(y)F_(z) gas selected from the group consisting of a C₄H₂F₆ gas, a C₄H₂F₈ gas, a C₃H₂F₄ gas, and a C₃H₂F₆ gas into the chamber to generate plasma to etch a dielectric film in a substrate supported on the substrate support. The control operation includes setting the substrate support at a temperature of 0° C. or lower and setting the HF gas to a flow rate greater than a flow rate of the C_(x)H_(y)F_(z) gas.

One or more embodiments of the present disclosure will now be described with reference to the drawings. In the figures, the same or similar components are given the same reference numerals, and may not be described repeatedly. Unless otherwise specified, the positional relationships shown in the drawings are used to describe the vertical, lateral, and other positions. The drawings are not drawn to scale relative to the actual ratio of each component, and the actual ratio is not limited to the ratio in the drawings.

Structure of Substrate Processing Apparatus 1

FIG. 1 is a schematic diagram of a substrate processing apparatus 1 according to one exemplary embodiment. A substrate processing method according to one exemplary embodiment (hereinafter referred to as the processing method) may be used by the substrate processing apparatus 1.

The substrate processing apparatus 1 shown in FIG. 1 includes a chamber 10. The chamber 10 has an internal space 10 s. The chamber 10 includes a chamber body 12 that is substantially cylindrical. The chamber body 12 is formed from, for example, aluminum. The chamber body 12 has an inner wall coated with an anticorrosive film. The anticorrosive film may be a film of ceramic such as aluminum oxide or yttrium oxide.

The chamber body 12 has a side wall having a port 12 p. The substrate W is transferred between the internal space 10 s and the outside of the chamber 10 through the port 12 p. The port 12 p is open and closed by a gate valve 12 g. The gate valve 12 g is on the side wall of the chamber body 12.

A support 13 is located on the bottom of the chamber body 12. The support 13 is formed from an insulating material. The support 13 is substantially cylindrical. The support 13 extends upward from the bottom of the chamber body 12 into the internal space 10 s. The support 13 supports a substrate support 14. The substrate support 14 supports the substrate W in the internal space 10 s.

The substrate support 14 includes a lower electrode 18 and an electrostatic chuck (ESC) 20. The substrate support 14 may further include an electrode plate 16. The electrode plate 16 is substantially disk-shaped and is formed from a conductor such as aluminum. The lower electrode 18 is on the electrode plate 16. The lower electrode 18 is substantially disk-shaped and is formed from a conductor such as aluminum. The lower electrode 18 is electrically coupled to the electrode plate 16.

The ESC 20 is on the lower electrode 18. The substrate W is placed on the upper surface of the ESC 20. The ESC 20 includes a body and an electrode. The body of the ESC 20 is substantially disk-shaped and is formed from a dielectric. In the ESC 20, the electrode is a film electrode located in the body. The electrode in the ESC 20 is coupled to a direct-current (DC) power supply 20 p through a switch 20 s. A voltage is applied from the DC power supply 20 p to the electrode in the ESC 20 to generate an electrostatic attraction between the ESC 20 and the substrate W. The substrate W is attracted to and held by the ESC 20 under the generated electrostatic attraction.

An edge ring 25 is placed on the substrate support 14. The edge ring 25 is annular. The edge ring 25 may be formed from silicon, silicon carbide, or quartz. The substrate W is placed in an area on the ESC 20 surrounded by the edge ring 25.

The lower electrode 18 has an internal channel 18 f in which a heat-exchange medium (e.g., a refrigerant) is supplied through a pipe 22 a from a chiller unit external to the chamber 10. The heat-exchange medium supplied to the channel 18 f returns to the chiller unit through a pipe 22 b. In the substrate processing apparatus 1, the temperature of the substrate W on the ESC 20 is adjusted through heat exchange between the heat-exchange medium and the lower electrode 18.

The substrate processing apparatus 1 includes a gas supply line 24. The gas supply line 24 supplies a heat-transfer gas (e.g., a He gas) from a heat-transfer gas supply assembly into a space between the upper surface of the ESC 20 and the back surface of the substrate W.

The substrate processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is located above the substrate support 14. The upper electrode 30 is supported in an upper portion of the chamber body 12 with a member 32. The member 32 is formed from an insulating material. The upper electrode 30 and the member 32 close a top opening of the chamber body 12.

The upper electrode 30 may include a ceiling plate 34 and a support member 36. The ceiling plate 34 has its lower surface exposed to and defining the internal space 10 s. The ceiling plate 34 may be formed from a low resistance conductor or a semiconductor that generates less Joule heat. The ceiling plate 34 has multiple gas outlet holes 34 a that are through-holes in the thickness direction.

The support member 36 supports the ceiling plate 34 in a detachable manner. The support member 36 is formed from a conductive material such as aluminum. The support member 36 has an internal gas-diffusion compartment 36 a. The support member 36 has multiple gas holes 36 b that extend downward from the gas-diffusion compartment 36 a. The gas holes 36 b communicate with the respective gas outlet holes 34 a. The support member 36 has a gas inlet 36 c. The gas inlet 36 c is connected to the gas-diffusion compartment 36 a. The gas inlet 36 c is also connected to a gas supply pipe 38.

The gas supply pipe 38 is connected to a set of gas sources 40 through a set of flow controllers 41 and a set of valves 42. The flow controller set 41 and the valve set 42 are included in a gas supply unit. The gas supply unit may further include the gas source set 40. The gas source set 40 includes multiple gas sources. The gas sources include the sources of the process gas used with the processing method. The flow controller set 41 includes multiple flow controllers. The flow controllers in the flow controller set 41 are mass flow controllers or pressure-based flow controllers. The valve set 42 includes multiple open-close valves. The gas sources in the gas source set 40 are connected to the gas supply pipe 38 through the respective flow controllers in the flow controller set 41 and through the respective open-close valves in the valve set 42.

The substrate processing apparatus 1 includes a shield 46 along an inner wall of the chamber body 12 and along the periphery of the support 13 in a detachable manner. The shield 46 prevents a reaction product from accumulating on the chamber body 12. The shield 46 includes, for example, an aluminum base coated with an anticorrosive film. The anticorrosive film may be a film of ceramic such as yttrium oxide.

A baffle plate 48 is located between the support 13 and the side wall of the chamber body 12. The baffle plate 48 includes, for example, an aluminum member coated with an anticorrosive film (e.g., an yttrium oxide film). The baffle plate 48 has multiple through-holes. The chamber body 12 has an outlet 12 e in its bottom below the baffle plate 48. The outlet 12 e is connected to an exhaust device 50 through an exhaust pipe 52. The exhaust device 50 includes a pressure control valve and a vacuum pump such as a turbomolecular pump.

The substrate processing apparatus 1 includes a radio-frequency (RF) power supply 62 and a bias power supply 64. The RF power supply 62 generates RF power HF. The RF power HF has a first frequency suitable for generating plasma. The first frequency ranges from, for example, 27 to 100 MHz. The RF power supply 62 is coupled to the lower electrode 18 through an impedance matching circuit, or matcher 66, and through the electrode plate 16. The matcher 66 includes a circuit for matching the impedance of a load (the lower electrode 18) for the RF power supply 62 and the output impedance of the RF power supply 62. The RF power supply 62 may be coupled to the upper electrode 30 through the matcher 66. The RF power supply 62 serves as an exemplary plasma generator.

The bias power supply 64 generates an electrical bias. The bias power supply 64 is electrically coupled to the lower electrode 18. The electrical bias has a second frequency lower than the first frequency. The second frequency ranges from, for example, 400 kHz to 13.56 MHz. When used in addition to the RF power HF, the electrical bias is applied to the substrate support 14 to draw ions toward the substrate W. In one example, the electrical bias is applied to the lower electrode 18. The electrical bias applied to the lower electrode 18 changes the potential of the substrate W on the substrate support 14 in periods defined by the second frequency. The electrical bias may be applied to a bias electrode located in the ESC 20.

In one embodiment, the electrical bias may be RF power LF with the second frequency. When used in addition to the RF power HF, the RF power LF serves as RF bias power for drawing ions toward the substrate W. The bias power supply 64 that generates RF power LF is coupled to the lower electrode 18 through an impedance matching circuit, or matcher 68, and through the electrode plate 16. The matcher 68 includes a circuit for matching the impedance of a load (the lower electrode 18) for the bias power supply 64 and the output impedance of the bias power supply 64.

The RF power LF alone may be used to generate plasma, without the RF power HF being used. In other words, a single source of RF power may be used to generate plasma. In this case, the RF power LF may have a frequency higher than 13.56 MHz, or for example, 40 MHz. In this case, the substrate processing apparatus 1 may not include the RF power supply 62 and the matcher 66. The bias power supply 64 serves as an exemplary plasma generator.

In another embodiment, the electrical bias may be a pulsed voltage. In this case, the bias power supply may be a DC power supply. The bias power supply may apply a pulsed voltage or may include a device for pulsing the voltage downstream from the bias power supply. In one example, a pulsed voltage is applied to the lower electrode 18 to cause the substrate W to have a negative potential. The pulsed voltage may have a square wave pulse, a triangular wave pulse, an impulse, or any other waveforms.

The pulsed voltage occurs in periods defined by the second frequency. Each period of the pulsed voltage includes two periods. The pulsed voltage is negative in one of the two periods. The voltage has a higher level (a greater absolute value) in one period than in the other period. The voltage may be negative or positive in the other period. The negative voltage in the other period may have a level higher than zero or a level of zero. In this embodiment, the bias power supply 64 is coupled to the lower electrode 18 through a low-pass filter and through the electrode plate 16. The bias power supply 64 may be coupled to the bias electrode in the ESC 20, instead of to the lower electrode 18.

In one embodiment, the bias power supply 64 may apply a continuous-wave electrical bias to the lower electrode 18. In other words, the bias power supply 64 may continuously apply the electrical bias to the lower electrode 18.

In some embodiments, the bias power supply 64 may apply a pulsed electrical bias to the lower electrode 18. The pulsed electrical bias may be periodically applied to the lower electrode 18. The pulsed electrical bias occurs in periods defined by a third frequency. The third frequency is lower than the second frequency. The third frequency ranges from, for example, 1 Hz to 200 kHz inclusive. In some embodiments, the third frequency may range from 5 Hz to 100 kHz inclusive.

Each period of the pulsed electrical bias includes two periods, or specifically, a period H and a period L. The electrical bias has a higher level (or a higher level of the pulsed electrical bias) in the period H than in the period L. In other words, the level of the electrical bias may be increased or decreased to apply a pulsed electrical bias to the lower electrode 18. The electrical bias may have a level higher than zero in the period L. In some embodiments, the electrical bias may have a level of zero in the period L. In other words, the pulsed electrical bias may be applied to the lower electrode 18 by repeatedly turning on and off the electrical bias applied to the lower electrode 18. When the electrical bias is RF power LF, the power level of the electrical bias is the same level as the power level of the RF power LF. The RF power LF used as the pulsed electrical bias has a level of 2 kW or more. When the electrical bias is a pulsed negative DC voltage, the power level of the electrical bias is a level equivalent to the effective value of the absolute value of the negative DC voltage. The duty ratio of the pulsed electrical bias, or the ratio of the period H to the period of the pulsed electrical bias, ranges from, for example, 1 to 80% inclusive. In some embodiments, the duty ratio of the pulsed electrical bias may range from 5 to 50% inclusive or 50 to 99% inclusive. Of the periods during which the electrical bias is applied, the period L corresponds to the first period described above, and the period H corresponds to the second period described above. The level of the electrical bias in the period L corresponds to zero or at the first level described above, and the level of the electrical bias in the period H corresponds to the second level described above.

In one embodiment, the RF power supply 62 may provide continuous-wave RF power HF. In other words, the RF power supply 62 may continuously provide the RF power HF.

In some embodiments, the RF power supply 62 may provide pulsed-RF power HF. The pulsed-RF power HF may be provided periodically. The pulsed-RF power HF occurs in periods defined by a fourth frequency. The fourth frequency is lower than the second frequency. In one embodiment, the fourth frequency is the same as the third frequency. Each period of the pulsed-RF power HF includes two periods, or specifically, a period H and a period L. The RF power HF has a higher power level in the period H than in the other period, or the period L. The RF power HF may have a power level higher than zero or a power level of zero in the period L. Of the periods during which the RF power HF is supplied, the period L corresponds to the third period described above, and the period H corresponds to the fourth period described above. The level of the RF power HF in the period L corresponds to zero or at the third level described above, and the level of the electrical bias in the period H corresponds to the fourth level described above.

The periods of the pulsed-RF power HF may be synchronized with the periods of the pulsed electrical bias. The periods H of the pulsed-RF power HF may be synchronized with the periods H of the pulsed electrical bias. In some embodiments, the periods H of the pulsed-RF power HF may not be synchronized with the periods H of the pulsed electrical bias. The periods H of the pulsed-RF power HF may have the same durations as or may have durations different from the periods H of the pulsed electrical bias. The periods H of the pulsed-RF power HF may partially or entirely overlap the periods H of the pulsed electrical bias.

FIG. 2 is a timing chart showing example RF power HF and an example electrical bias. In FIG. 2 , the RF power HF and the electrical bias are both provided in pulses. In FIG. 2 , the horizontal axis indicates time. In FIG. 2 , the vertical axis indicates the power level of the RF power HF and the power level of the electrical bias. The RF power HF at L1 indicates the RF power HF not being provided or being provided at a power level lower than at H1. The electrical bias at L2 indicates the electrical bias not being applied or being applied at a power level lower than at H2. When the electrical bias is a pulsed negative DC voltage, the power level of the electrical bias is a level equivalent to the effective value of the absolute value of the negative DC voltage. The power level of the RF power HF and the power level of the electrical bias shown in FIG. 2 do not represent the relative relationship between them, but may be set as appropriate. In the example in FIG. 2 , the periods of the pulsed-RF power HF are synchronized with the periods of the pulsed electrical bias. The periods H of the pulsed-RF power HF have the same durations as the periods H of the pulsed electrical bias, and the periods L of the pulsed-RF power HF have the same durations as the periods L of the pulsed electrical bias.

Referring back to FIG. 1 , the substrate processing apparatus 1 further includes a power supply 70. The power supply 70 is coupled to the upper electrode 30. In one embodiment, the power supply 70 may provide a DC voltage or low-frequency power to the upper electrode 30 during the plasma processing. For example, the power supply 70 may provide a negative DC voltage or periodically provide low-frequency power to the upper electrode 30. The DC voltage or the low-frequency power may be provided in pulses or continuously. In this embodiment, positive ions in the internal space 10 s for plasma processing are attracted to and collide with the upper electrode 30. This causes secondary electrons to be emitted from the upper electrode 30. The emitted secondary electrons modify a mask film MK and improve the etching resistance of the mask film MK. Secondary electrons also increase the plasma density. The emitted secondary electrons neutralize the charged substrate W, thus allowing more ions to be directed straight into recesses formed by etching. For the upper electrode 30 formed from a silicon-containing material, silicon is emitted together with secondary electrons upon collision of the positive ions. The emitted silicon combines with oxygen in the plasma and is deposited on the mask as a silicon oxide compound, serving as a protective film. As described above, the DC voltage or the low-frequency power provided to the upper electrode 30 reduces feature failures in the recesses formed by etching and improves the etching rate, in addition to improving the selectivity.

The gas supply unit supplies a gas into the internal space 10 s for plasma processing in the substrate processing apparatus 1. The RF power HF, the electrical bias, or both are provided to form an RF electric field between the upper electrode 30 and the lower electrode 18. The resultant RF electric field generates plasma from the gas in the internal space 10 s.

The substrate processing apparatus 1 may further include a controller 80. The controller 80 may be a computer including a processor, a storage such as a memory, an input device, a display, and an input-output interface for signals. The controller 80 controls the components of the substrate processing apparatus 1. An operator can use the input device in the controller 80 to input a command or perform other operations for managing the substrate processing apparatus 1. The display in the controller 80 can display and visualize the operating state of the substrate processing apparatus 1. The storage stores control programs and recipe data. The control program is executed by the processor to perform the processing in the substrate processing apparatus 1. The processor executes the control program to control the components of the substrate processing apparatus 1 in accordance with the recipe data. In one exemplary embodiment, the controller 80 may be partially or entirely included in a device external to the substrate processing apparatus 1.

Structure of Substrate Processing System PS

FIG. 3 is a schematic diagram of a substrate processing system PS according to one exemplary embodiment. The processing method may be used by the substrate processing system PS.

The substrate processing system PS includes substrate processing chambers PM1 to PM6 (hereinafter also collectively referred to as the substrate processing modules PM), a transfer module TM, loadlock modules LLM1 and LLM2 (hereinafter also collectively referred to as the loadlock modules LLM), a loader module LM, and load ports LP1 to LP3 (hereinafter also collectively referred to as the load ports LP). A controller CT controls the components of the substrate processing system PS to perform predetermined processing on a substrate W.

Each substrate processing module PM performs etching, trimming, film deposition, annealing, doping, lithography, cleaning, ashing, and other processing on the substrate W inside the substrate processing module PM. The substrate processing modules PM may include a measurement module that may measure, for example, the thickness of a film formed on the substrate W and the dimensions of a pattern formed on the substrate W. The substrate processing apparatus 1 shown in FIG. 1 is an example of the substrate processing module PM.

The transfer module TM includes a transfer device that transfers the substrate W between the substrate processing modules PM or between a substrate processing module PM and a loadlock module LLM. The substrate processing modules PM and the loadlock modules LLM are located adjacent to the transfer module TM. The transfer module TM, the substrate processing modules PM, and the loadlock modules LLM are spatially isolated or connected through gate valves that can be open and closed.

The loadlock modules LLM1 and LLM2 are located between the transfer module TM and the loader module LM. Each loadlock module LLM can switch its internal pressure between an ambient atmosphere and a vacuum atmosphere. The loadlock module LLM transfers the substrate W from the loader module LM, which is in the ambient atmosphere, to the transfer module TM, which is in the vacuum atmosphere, or from the transfer module TM, which is in the vacuum atmosphere, to the loader module LM, which is in the ambient atmosphere.

The loader module LM includes a transfer device that transfers the substrate W between the loadlock module LLM and a load port LP. The load port LP can receive, for example, a front-opening unified pod (FOUP) that can store 25 substrates W or an empty FOUP. The loader module LM unloads a substrate W from the FOUP in the load port LP and transfers the substrate W to the loadlock module LLM. The loader module LM unloads a substrate W from the loadlock module LLM and transfers the substrate W to the FOUP in the load port LP.

The controller CT controls the components of the substrate processing system PS to perform predetermined processing on the substrate W. The controller CT stores recipes containing process procedures, process conditions, transfer conditions, or other sets of data. The controller CT controls the components of the substrate processing system PS to perform predetermined processing on a substrate W in accordance with the recipes. The controller CT may implement a part or all of the functions of the controller 80 in the substrate processing apparatus 1 shown in FIG. 1 .

Exemplary Substrate W

FIG. 4 is a diagram of the substrate W showing an example cross-sectional structure. The substrate W is an example substrate on which the processing method may be performed. The substrate W includes a dielectric film DF. The substrate W may include an underlying film UF and a mask film MK. As shown in FIG. 4 , the substrate W may be formed by stacking the underlying film UF, the dielectric film DF, and the mask film MK in this order.

The underlying film UF may be, for example, a silicon wafer or an organic film, a dielectric film, a metal film, or a semiconductor film formed on the silicon wafer. The underlying film UF may include multiple films stacked on one another.

The dielectric film DF may be a silicon-containing film. Examples of the silicon-containing film include a silicon oxide film, a silicon nitride film, a silicon oxynitride film (SiON film), and a silicon-containing antireflective coating (Si-ARC) film. The dielectric film DF may include a polycrystalline silicon film. The dielectric film DF may include multiple films stacked on one another. For example, the dielectric film DF may include silicon oxide films and polycrystalline silicon films that are alternately stacked on one another. In one example, the dielectric film DF may be a stacked film including silicon oxide films and silicon nitride films that are alternately stacked on one another.

The underlying film UF, the dielectric film DF, or both the films may be formed by a method such as chemical vapor deposition (CVD) and spin coating. The underlying film UF, the dielectric film DF, or both the films may be a flat film or an uneven film.

The mask film MK is formed on the dielectric film DF. The mask film MK defines at least one opening OP on the dielectric film DF. The opening OP is a space on the dielectric film DF and is surrounded by a side wall S1 of the mask film MK. In other words, in FIG. 4 , the dielectric film DF has an area covered by the mask film MK and an area exposed at the bottom of the opening OP.

The opening OP may have any feature in a plan view of the substrate W (when the substrate W is viewed from the top toward the bottom in FIG. 4 ). The opening feature may be, for example, a hole, a line, or a combination of a hole and a line. The mask film MK may have multiple side walls S1 that may define multiple openings OP. The multiple openings OP may be slits arranged in a pattern of lines and spaces at regular intervals. The multiple openings OP may be holes arranged in a patterned array.

The mask film MK is, for example, an organic film or a metal-containing film. Examples of the organic film include a spin-on carbon (SOC) film, an amorphous carbon film, and a photoresist film. The metal-containing film may contain, for example, tungsten, tungsten carbide, or titanium nitride. The mask film MK may be formed by CVD, spin coating or, other methods. The opening OP may be formed by etching the mask film MK. The mask film MK may be formed by lithography.

In one example, the substrate W may include, as the dielectric film DF, a stacked film including silicon oxide films and silicon nitride films on the underlying film UF. In one example, the substrate W may include, as the mask film MK, a polycrystalline silicon film, silicon boride, or tungsten carbide on the silicon nitride films. The mask film MK may be a multilayer resist containing a polycrystalline silicon film, silicon boride, or tungsten carbide. In one example, the multilayer resist includes a mask including a hard mask on the polycrystalline silicon film. In one example, the hard mask includes a silicon oxide film (a tetraethoxysilane, or TEOS film). The silicon nitride films in the stacked film may be etched using the hard mask as a mask, and the silicon oxide films in the stacked film may be etched using a polycrystalline silicon film as a mask.

Exemplary Processing Method

FIG. 5 is a flowchart of the processing method. The processing method includes providing a substrate (step ST1) and etching (step ST2). The controller 80 shown in FIG. 1 controls the components of the substrate processing apparatus 1 to perform the processing method on a substrate W shown in FIG. 4 .

Step ST1: Providing Substrate

In step ST1, a substrate W is provided in the internal space 10 s of the chamber 10. In the internal space 10 s, the substrate W is placed on the upper surface of the substrate support 14 and held by the ESC 20. The processing for forming each component of the substrate W may be at least partly performed in the internal space 10 s. All or a part of the components of the substrate W may be formed in a device or a chamber external to the substrate processing apparatus 1. The resultant substrate W may then be loaded into the internal space 10 s and placed on the upper surface of the substrate support 14.

Step ST2: Etching

In step ST2, the dielectric film DF in the substrate W is etched. Step ST2 includes supplying a process gas (step ST21) and generating plasma (step ST22). The dielectric film DF is etched with an active species (ions or radicals) in plasma generated from the process gas.

In step ST21, the gas supply unit supplies the process gas into the internal space 10 s. The process gas contains a reaction gas containing a fluorine-containing gas and a C_(x)H_(y)F_(z) (a gas different from the fluorine-containing gas described above, where x is an integer greater than or equal to 2, and y and z are integers greater than or equal to 1) gas (hereinafter also referred to as a C_(x)H_(y)F_(z) gas). In the present embodiment, the reaction gas does not include any noble gas such as Ar, unless otherwise stated.

The fluorine-containing gas may be a gas that can produce HF species in the chamber 10 during plasma processing. The HF species include at least one of a hydrogen fluoride gas, radicals, or ions. In one example, the fluorine-containing gas may be an HF gas or a hydrofluorocarbon gas. The fluorine-containing gas may be a mixture of gases containing hydrogen and fluorine sources. The hydrogen source may be, for example, H₂, NH₃, H₂O, H₂O₂, or hydrocarbon (e.g., CH₄ or C₃H₆). The fluorine source may be NF₃, SF₆, WF₆, XeF₂, fluorocarbon, or hydrofluorocarbon. The fluorine-containing gas is hereinafter also referred to as an HF-based gas. The plasma generated from the process gas containing an HF-based gas contains many HF species (etchant). The flow rate of the HF-based gas may be higher than the flow rate of the C_(x)H_(y)F_(z) gas. The HF-based gas may be a main etchant gas. The HF-based gas may have the highest flow rate as a percentage of the total flow rate of the reaction gas, for example, higher than or equal to 70% by volume of the total flow rate of the reaction gas. The HF-based gas may be less than or equal to 96% by volume of the total flow of the reaction gas.

The C_(x)H_(y)F_(z) gas can use, for example, a C_(x)H_(y)F_(z) (where x is an integer greater than or equal to 2, and y and z are integers greater than or equal to 1) gas. The C_(x)H_(y)F_(z) (where x is an integer greater than or equal to 2, and y and z are integers greater than or equal to 1) gas may contain at least one selected from the group consisting of a C₂HF₅ gas, a C₂H₂F₄ gas, a C₂H₃F₃ gas, a C₂H₄F₂ gas, a C₃HF₇ gas, a C₃H₂F₂ gas, a C₃H₂F₄ gas, a C₃H₂F₆ gas, a C₃H₃F₅ gas, a C₄H₂F₆ gas, a C₄H₅F₅ gas, a C₄H₂F₈ gas, a C₅H₂F₆ gas, a C₅H₂F₁₀ gas, and a C₅H₃F₇ gas. In one example, the C_(x)H_(y)F_(z) gas may be at least one selected from the group consisting of a C₃H₂F₄ gas, a C₃H₂F₆ gas, a C₄H₂F₆ gas, and a C₄H₂F₈ gas. In another example, the C_(x)H_(y)F_(z) gas may be at least one selected from the group consisting of a C₃H₂F₄ gas, a C₃H₂F₆ gas, a C₄H₂F₆ gas, a C₄H₂F₈ gas, and a C₅H₂F₆ gas. For a C₄H₂F₆ gas as the C_(x)H_(y)F_(z) gas, for example, C₄H₂F₆ may be linear or cyclic.

The plasma generated from the process gas containing the C_(x)H_(y)F_(z) gas contains C_(x)H_(y)F_(z) species that dissociate from the C_(x)H_(y)F_(z) gas. The C_(x)H_(y)F_(z) species include many C_(x)H_(y)F_(z) radicals containing two or more carbon atoms (e.g., C₂H₂F radicals, C₂H₂F₂ radicals, and C₃HF₃ radicals, hereinafter referred to as C_(x)H_(y)F_(z)-based radicals). The C_(x)H_(y)F_(z) radicals form a protective film on the surface of the mask film MK to protect the surface. The protective film may reduce the likelihood of the mask film MK being etched in etching the dielectric film DF. The C_(x)H_(y)F_(z)-based radicals thus may improve the selectivity (a value obtained by dividing the etching rate of the dielectric film DF by the etching rate of the mask film MK) of the dielectric film DF to the mask film MK in etching the dielectric film DF.

The plasma generated from the process gas containing the C_(x)H_(y)F_(z) gas contains many hydrogen fluoride (HF) species dissociated from the C_(x)H_(y)F_(z) gas, many HF species further dissociated from the C_(x)H_(y)F_(z)-based radicals, or many HF species dissociated from both the C_(x)H_(y)F_(z) gas and the C_(x)H_(y)F_(z)-based radicals. The HF species include at least one of a hydrogen fluoride gas, radicals, or ions. The HF species serve as an etchant for the dielectric film DF. The etching rate of the dielectric film DF can be improved by many HF species contained in the plasma.

The C_(x)H_(y)F_(z) gas may include one or more CF₃ groups. When the C_(x)H_(y)F_(z) gas includes the CF₃ group, and, for example, the single CH group is bonded to the CF₃ group, the molecular structure of the C_(x)H_(y)F_(z) gas allows HF to be easily dissociated and allows the plasma to contain more HF species.

The process gas may contain a C_(x)F_(z) (where x is an integer greater than or equal to 2, and z is an integer greater than or equal to 1) gas in place of part or all of the C_(x)H_(y)F_(z) gas described above. More specifically, the C_(x)F_(z) gas may be at least one selected from the group consisting of C₂F₂, C₂F₄, C₃F₈, C₄F₆, C₄F₈, and C₅F₈. This can reduce the amount of hydrogen in the plasma and may reduce the likelihood of, for example, morphology deteriorating and moisture in the chamber 10 increasing with excess hydrogen. The term morphology herein refers to the characteristics associated with the feature of the mask such as the surface condition of the mask film MK and the roundness of the opening OP.

The flow rate of the C_(x)H_(y)F_(z) gas is less than or equal to 20% by volume of the total flow rate of the reaction gas. The flow rate of the C_(x)H_(y)F_(z) gas may be, for example, lower than or equal to 15% by volume, less than or equal to 10% by volume, or less than or equal to 5% by volume of the total flow rate of the reaction gas.

The reaction gas may contain a halogen-containing gas. The halogen-containing gas may allow adjustment of the features of the mask film MK and the dielectric film DF in etching. The halogen-containing gas may be at least one of a chlorine-containing gas, a bromine-containing gas, or an iodine-containing gas. The chlorine-containing gas may be a gas such as Cl₂, SiCl₂, SiCl₄, CCl₄, SiH₂Cl₂, Si₂Cl₆, CHCl₃, SO₂Cl₂, BCl₃, PCl₃, PCl₅, and POCl₃. The bromine-containing gas may be a gas such as Br₂, HBr, CBr₂F₂, C₂F₅Br, PBr₃, PBr₅, POBr₃, and BBr₃. The iodine-containing gas may be a gas such as HI, CF₃I, C₂F₅I, C₃F₇I, IF₅, IF₇, I₂, and PI₃. In one example, the halogen-containing gas may be at least one selected from the group consisting of a Cl₂ gas, a Br₂ gas, an HBr gas, a CF₃I gas, an IF₇ gas, and C₂F₅Br gas. In another example, the halogen-containing gas may be a Cl₂ gas or an HBr gas.

The reaction gas may contain a nitrogen-containing gas. The nitrogen-containing gas may reduce the likelihood of the blockage of the opening OP in the mask film MK in etching. The nitrogen-containing gas may be, for example, at least one selected from the group consisting of an NF₃ gas, an N₂ gas, and an NH₃ gas.

The reaction gas may contain an oxygen-containing gas. The oxygen-containing gas may reduce the likelihood of blockage of the mask film MK in etching, similarly to a nitrogen-containing gas. The oxygen-containing gas may contain, for example, at least one gas selected from the group consisting of O₂, CO, CO₂, H₂O, and H₂O₂. In one example, the reaction gas contains an oxygen-containing gas other than H₂O, or specifically, at least one gas selected from the group consisting of O₂, CO, CO₂, and H₂O₂. The oxygen-containing gas may cause less damage to the mask film MK and may reduce the likelihood of morphological deterioration.

FIG. 6 is a diagram of example features of mask films MK after etching. FIG. 6 shows example features of the mask films MK (in a plan view) on sample substrates with the same structure as the substrate W etched in the substrate processing apparatus 1. In FIG. 6 , the No. field shows the sample number for each etched sample substrate. The Process Gas field shows each process gas used for etching. In this field, A indicates a process gas (hereinafter, process gas A) containing an HF gas, a C₄H₂F₆ gas, an O₂ gas, an NF₃ gas, an HBr gas, and a Cl₂ gas. The process gas A contains greater than or equal to 80% by volume of the HF gas of the total flow rate of the reaction gas and 4 to 5% by volume of the O₂ gas of the total flow rate of the reaction gas. In the Process Gas field, B indicates a process gas (hereinafter, process gas B) with the same compositions as the process gas A but excluding an NF₃ gas and thus having a higher flow rate of the O₂ gas to compensate the flow rate of the NF₃ gas. The process gas B contains 6 to 7% by volume of the O₂ gas of the total flow rate of the reaction gas. The Voltage to Upper Electrode field either shows Yes, indicating that a DC voltage with negative polarity is provided to the upper electrode 30 in the substrate processing apparatus 1 during etching, or shows No, indicating that the DC voltage with negative polarity is not provided to the upper electrode 30. The Mask Feature field in FIG. 6 reveals that, when the process gas A containing NF₃ is used (samples 1 and 3), the openings OP have lower roundness irrespective of whether the Voltage to Upper Electrode field shows Yes or No and steps are observed on the surface of the mask film MK. In contrast, when the process gas B containing no NF₃ gas and having a higher flow rate of the O₂ gas is used (samples 2 and 4), the openings OP have higher roundness, and no steps are observed on the surface of the mask film MK, showing that the morphology of the mask film MK is improved, as compared with when the process gas A is used (samples 1 and 3).

The reaction gas may contain a phosphorus-containing gas. The phosphorus-containing gas may contain at least one gas selected from the group consisting of PF₃, PF₅, POF₃, HPF₆, PCl₃, PCl₅, POCl₃, PBr₃, PBr₅, POBr₃, PI₃, P₄O₁₀, P₄O₈, P₄O₆, PH₃, Ca₃P₂, H₃PO₄, and Na₃PO₄. Of these gases, the phosphorus-containing gas may be a phosphorus halide-containing gas such as a gas containing PF₃, PF₅, or PCl₃, or a fluoride gas such as a gas containing PF₃ or PF₅.

The process gas may contain a boron-containing gas such as BF₃, BCl₃, BBr₃, and B₂H₆. The process gas may also contain a sulfur-containing gas such as SF₆ and COS.

The process gas may contain an inert gas (a noble gas such as Ar) in addition to the reaction gas described above.

The pressure of the process gas supplied into the internal space 10 s is adjusted by controlling the pressure control valve of the exhaust device 50 connected to the chamber body 12. The pressure of the process gas may be, for example, from 5 to 100 mTorr (0.7 to 13.3 Pa) inclusive, from 10 to 60 mTorr (1.3 to 8.0 Pa) inclusive, or from 20 to 40 mTorr (2.7 to 5.3 Pa) inclusive.

In step ST22, the plasma generator (the RF power supply 62, the bias power supply 64, or both) provides the RF power, the electrical bias, or both. This generates an RF electric field between the upper electrode 30 and the substrate support 14 to generate plasma from the process gas in the internal space 10 s. An active species such as ions and radicals in the generated plasma are attracted to the substrate W to etch the substrate W.

In step ST22, the substrate support 14 is set at a temperature of 0° C. or lower. The temperature of the substrate support 14 may be set at, for example, 0° C. or lower, or 0, −10, −20, −30, −40, −60, or −70° C. or lower. The temperature of the substrate support 14 is adjustable by the heat-exchange medium supplied from the chiller unit.

FIG. 7 is a graph showing an example of temperature dependence of etching. FIG. 7 shows the experimental results from etching a silicon oxide film by generating plasma from the process gas that is a mixture of a hydrogen fluoride gas and an argon gas using the plasma processing apparatus 1. In this experiment, the silicon oxide film was etched while the temperature of the substrate support 14 was being changed. The amounts of HF and SiF₃ in the gas phase were measured using a quadrupole mass analyzer during the etching of the silicon oxide film. In FIG. 7 , the horizontal axis indicates the temperature T (° C.) of the substrate support 14, and the vertical axis indicates the amounts of HF and SiF₃ (intensity with reference to helium).

As shown in FIG. 7 , the amount of HF as an etchant decreased, and the amount of SiF₃ as a reaction product generated by etching the silicon oxide film increased when the temperature of the substrate support 14 was at about −60° C. or lower. In other words, in this experiment, the amount of the etchant used in etching the silicon oxide film increased when the temperature of the substrate support 14 was at about −60° C. or lower.

Thus, this experiment reveals that the etching of the silicon oxide film proceeds to improve the selectivity of the dielectric film DF to the mask film MK as the temperature of the substrate support 14 is lower. The temperature at which the amount of the etchant increases varies depending on the processing conditions including the flow ratio of the hydrogen fluoride gas in the reaction gas and an additive gas. Thus, the temperature of the substrate support 14 may be set based on the results from examining the relationship between the temperature of the substrate support 14 and the amounts of HF and SiF₃ under specific conditions.

FIG. 8 is a diagram of the substrate Win step ST22 showing an example cross-sectional structure. During the processing in step ST22, the mask film MK serves as a mask, and a portion of the dielectric film DF corresponding to the opening OP in the mask film MK is etched in the depth direction (from the top to the bottom in FIG. 8 ) to form the recess RC. The recess RC is a space surrounded by the side wall S1 of the mask film MK and a side wall S2 of the dielectric film DF. The recess RC formed in step ST22 may have an aspect ratio of 20 or more, or 30, 40, 50, or 100 or more.

With the processing method, the reaction gas contains the C_(x)H_(y)F_(z) gas. The C_(x)H_(y)F_(z) gas produces high-density C_(x)H_(y)F_(z)-based radicals in the plasma. The C_(x)H_(y)F_(z)-based radicals are adsorbed on the surface of the mask film MK (an upper surface T1 and the side wall S1) and on the side wall S2 of the dielectric film DF to form a protective film PF. The protective film PF may be thinner in the depth direction (from the top to the bottom in FIG. 8 ). The protective film PF reduces the likelihood of the surface of the mask film MK being removed by etching (specifically, the etching rate of the mask film MK increasing) during the processing in step ST22. This improves the selectivity of the dielectric film DF to the mask film MK.

The protective film PF may reduce the likelihood of the dielectric film DF being etched in the lateral direction (right-left direction in FIG. 8 ). At the flow rate of the C_(x)H_(y)F_(z) gas less than or equal to 20% by volume of the total flow rate of the reaction gas, this structure may further reduce the likelihood of excess deposition of carbon on the side wall S1 of the mask film MK, on the dielectric film DF, or on both the films as well as blockage of the opening OP in the mask film MK. For the reaction gas containing an oxygen-containing gas, this structure may further reduce the likelihood of excess deposition of carbon on the side wall S1 of the mask film MK, on the dielectric film DF, or on both the films as well as blockage of the opening OP in the mask film MK. At least one of the above factors allows the feature, the dimensions, or both of the recess RC in the dielectric film DF to be maintained as appropriate.

The C_(x)H_(y)F_(z) gas produces many HF species in the plasma. During the processing in step ST22, the HF species (etchant) may thus be sufficiently supplied to a bottom BT of the recess RC formed in the dielectric film DF. During the processing in step ST22, the substrate support 14 is controlled to a lower temperature of 0° C. or lower. The adsorption of the HF species (etchant) at the bottom BT of the recess RC is facilitated by reducing an increase in the temperature of the substrate W (HF species have a higher adsorption coefficient at a lower temperature). At least one of the above factors improves the etching rate of the dielectric film DF.

In step ST22, when plasma is being generated in the internal space 10 s, the bias power supply 64 may periodically apply a pulsed electrical bias to the substrate support 14. The periodic pulsed electrical bias may allow etching and formation of the protective film PF to proceed alternately.

The flow rate of the C_(x)H_(y)F_(z) gas supplied into the internal space 10 s may be varied during the processing in step ST2. For example, first etching may be performed with a reaction gas containing the C_(x)H_(y)F_(z) gas under a first partial pressure, and then second etching may be performed with a reaction gas containing the C_(x)H_(y)F_(z) gas under a second partial pressure. For the dielectric film DF being a stacked film of different materials, for example, this may allow appropriate etching of the stacked film by controlling the flow rate of the C_(x)H_(y)F_(z) gas based on the material of the film to be etched.

The flow rate of the C_(x)H_(y)F_(z) gas supplied into the internal space 10 s during the processing in step ST2 may differ between the center and the periphery of the substrate W in a plan view of the substrate W. Thus, when the dimensions of the openings OP each surrounded by the side wall S1 of the mask film MK differ between the center and the periphery of the substrate W, such dimensional variations may be corrected by controlling the distribution of the flow rate of the C_(x)H_(y)F_(z) gas.

The pressure in the chamber 10 (internal space 10 s) and the electrical bias applied to the substrate support 14 from the bias power supply 64 may be changed during the processing in step ST2. For example, step ST2 may include a first process and a second process. In the first process, the chamber 10 is set to a first pressure, a first electrical bias is applied to the substrate support 14, and the dielectric film DF is etched. In the second process, the chamber 10 is set to a second pressure, a second electrical bias is applied to the substrate support 14, and the dielectric film DF is etched. In step ST2, the first and second processes may be repeated alternately. The first pressure may differ from the second pressure, and may be, for example, higher than the second pressure. The first electrical bias may differ from the second electrical bias. For example, the absolute value of the first electrical bias may be greater than the absolute value of the second electrical bias. The first pressure, the second pressure, the first electrical bias, and the second electrical bias may be adjusted as appropriate to etch, for example, the dielectric film DF anisotropically until or immediately before the recess RC reaches the underlying film UF in the first process, and also to etch the bottom of the recess RC isotropically to expand laterally in the second process.

Experiments for evaluating the processing method will now be described below. The present disclosure is not limited to the experiments below.

Experiment 1

FIG. 9 is a graph showing the measurement results of Experiment 1. In Experiment 1, the amount of HF species produced in various reaction gases was measured. In Experiment 1, one of a C₄H₂F₆ gas, a C₄F₈ gas, a C₄F₆ gas, or a CH₂F₂ gas and an Ar gas were supplied as a reaction gas into the internal space 10 s of the substrate processing apparatus 1 to generate plasma for 10 minutes. The HF intensity before and after the plasma generation was then measured with the quadrupole mass analyzer. The temperature of the substrate support 14 was set at −40° C. The vertical axis in FIG. 9 indicates the difference between the HF intensity before the plasma generation and the HF intensity after the plasma generation. As the value on the vertical axis is greater, the amount of HF species produced in the plasm is greater.

As shown in FIG. 9 , the C₄H₂F₆ gas as one example of the reaction gas with the processing method produced more HF species in the plasma than the C₄F₈ and C₄F₆ gases without hydrogen elements, and also than the CH₂F₂ gas with hydrogen elements.

Experiment 2

FIGS. 10 and 11 are graphs showing the measurement results of Experiment 2. In Experiment 2, the etching rate and the selectivity with each of various process gases were measured. In Experiment 2, a sample substrate having the same structure as the substrate W was placed on the substrate support 14. The sample substrate includes silicon oxide as the dielectric film DF and an organic film as the mask film MK on the silicon film. A process gas was supplied into the internal space 10 s of the substrate processing apparatus 1 to generate plasma to etch the dielectric film DF in the sample substrate. The temperature of the substrate support 14 was set at −40° C. As shown in FIGS. 10 and 11 , with the reaction gas in the process gas containing any of a C₄F₈ gas, a CH₂F₂ gas, or a C₄H₂F₆ gas, the etching rate of the dielectric film DF (E/R (nm/min) in FIG. 10 ) and the selectivity of the dielectric film DF to the mask film MK (Sel. in FIG. 11 ) were measured. The flow rate of the C₄F₈ gas was 5% by volume of the total flow rate of the reaction gas. The flow rate of the CH₂F₂ gas was 15% by volume of the total flow rate of the reaction gas. The flow rate of the C₄H₂F₆ gas was 5% by volume of the total flow rate of the reaction gas. The reaction gas contained 70 to 90% by volume of the HF gas of the total flow rate of the reaction gas.

As shown in FIGS. 10 and 11 , the process gas containing the C₄H₂F₆ gas as an example of the reaction gas with the processing method shows a higher etching rate and higher selectivity than the process gas containing the C₄F₈ gas or the CH₂F₂ gas as the reaction gas.

Experiment 3

FIGS. 12 and 13 are graphs showing the results of Experiment 3. In Experiment 3, the etching rate and the bowing CD with various process gases were measured when the aspect ratio of the recess RC was changed. In Experiment 3, a sample substrate having the same structure as the substrate W in Experiment 2 was placed on the substrate support 14. A process gas was supplied into the internal space 10 s of the substrate processing apparatus 1 to generate plasma to etch the dielectric film DF in the sample substrate. The temperature of the substrate support 14 was set at −40° C. FIGS. 12 and 13 show the relationship between the selectivity of the dielectric film DF to the mask film MK when the aspect ratio (AR) of the recess RC was changed (Sel. in FIG. 12 ) and the maximum width of the recess RC of the dielectric film DF (bowing CD: CD_(m) (nm) in FIG. 13 ) when the reaction gas in the process gas contained either a C₄F₈ gas or a C₄H₂F₆ gas. The selectivity can be determined by dividing the etching rate of the dielectric film DF by the etching rate of the mask film MK. The C₄F₈ gas or the C₄H₂F₆ gas was 5% by volume of the total flow of the reaction gas. The reaction gas contained greater than or equal to 90% by volume of the HF gas of the total flow rate of the reaction gas.

As shown in FIGS. 12 and 13 , for the reaction gas containing the C₄H₂F₆ gas as an example of the process gas with the processing method, the high selectivity was maintained and an increase in the bowing CD was reduced compared with when the reaction gas containing the C₄F₈ gas was used, although the aspect ratio of the recess RC formed in the dielectric film DF was increased.

Experiment 4

FIG. 14 is a graph showing the measurement results of Experiment 4. In Experiment 4, a change in the emission spectral intensity of CO (CO intensity) over time was measured when the chamber 10 in the substrate processing apparatus 1 was cleaned with an oxygen gas. In FIG. 14 , CH1 indicates the chamber after the sample substrate with the same structure as in Experiment 2 was etched using the process gas containing 4% of the C₄H₂F₆ gas by volume of the total flow rate of the reaction gas. CH2 indicates the chamber after the sample substrate with the same structure as in Experiment 2 was etched using the process gas containing 16% of the CH₂F₂ gas by volume of the total flow rate of the reaction gas. The CO intensity is measured when a cleaning gas (oxygen gas) reacts with a carbon-containing deposit in the chamber 10 and can be used as an indication of the progress in cleaning in the chamber.

As shown in FIG. 14 , the CO intensity for the chamber CH1 reached the peak of the CO intensity immediately after the start of cleaning and then decreased rapidly, reaching zero at 20 to 30 seconds after the start of cleaning. The CO intensity for the chamber CH2 showed a lower peak value than for the CH1 and decreased more slowly, without reaching zero at 200 seconds after the start of cleaning. In other words, when the process gas containing the C₄H₂F₆ gas as an example of the reaction gas with the processing method was used, the chamber cleaning time after etching was shortened as compared with when the process gas containing the CH₂F₂ gas was used.

The above embodiments further include the aspects described below.

APPENDIX 1

An etching gas composition, comprising:

-   -   a reaction gas containing         -   an HF gas; and         -   at least one C_(x)H_(y)F_(z) gas selected from the group             consisting of a C₄H₂F₆ gas, a C₄H₂F₈ gas, a C₃H₂F₄ gas, and             a C₃H₂F₆ gas,     -   wherein the HF gas has a flow rate greater than a flow rate of         the C_(x)H_(y)F_(z) gas.

APPENDIX 2

The etching gas composition according to appendix 1, wherein

-   -   the flow rate of the C_(x)H_(y)F_(z) gas is less than or equal         to 20% by volume of a total flow rate of the reaction gas.

APPENDIX 3

The etching gas composition according to appendix 1 or appendix 2, wherein

-   -   the flow rate of the HF gas is greater than or equal to 70% by         volume of a total flow rate of the reaction gas.

APPENDIX 4

The etching gas composition according to any one of appendixes 1 to 3, wherein

-   -   the reaction gas further contains a halogen-containing gas.

APPENDIX 5

The etching gas composition according to appendix 4, wherein

-   -   the halogen-containing gas is at least one selected from the         group consisting of a chlorine-containing gas, a         bromine-containing gas, and an iodine-containing gas.

APPENDIX 6

The etching gas composition according to appendix 4, wherein

-   -   the halogen-containing gas is at least one gas selected from the         group consisting of Cl₂, SiCl₂, SiCl₄, CCl₄, SiH₂Cl₂, Si₂Cl₆,         CHCl₃, SO₂Cl₂, BCl₃, PCl₃, PCl₅, POCl₃, Br₂, HBr, CBr₂F₂,         C₂F₅Br, PBr₃, PBr₅, POBr₃, BBr₃, HI, CF₃I, C₂F₅I, C₃F₇I, IF₅,         IF₇, I₂, and PI₃.

APPENDIX 7

The etching gas composition according to any one of appendixes 1 to 5, wherein

-   -   the reaction gas contains a phosphorus-containing gas.

APPENDIX 8

The etching gas composition according to any one of appendixes 1 to 7, wherein

-   -   the reaction gas further contains an oxygen-containing gas.

APPENDIX 9

The etching gas composition according to any one of appendixes 1 to 8, wherein

-   -   the reaction gas further contains at least one selected from the         group consisting of a boron-containing gas and a         sulfur-containing gas.

The processing method may be modified in various ways without departing from the spirit and scope of the present disclosure. For example, the processing method may be performed with, in addition to the substrate processing apparatus 1 using capacitively coupled plasma, a substrate processing apparatus using any plasma source for, for example, inductively coupled plasma or microwave plasma.

REFERENCE SIGNS LIST

-   1 Substrate processing apparatus -   10 Chamber -   10 s Internal space -   12 Chamber body -   14 Substrate support -   16 Electrode plate -   18 Lower electrode -   20 Electrostatic chuck (ESC) -   30 Upper electrode -   50 Exhaust device -   62 Radio-frequency (RF) power supply -   64 Bias power supply -   80 Controller -   CT Controller -   DF Dielectric film -   MK Mask film -   OP Opening -   PF Protective film -   RC Recess -   UF Underlying film -   W Substrate 

1. A substrate processing method, comprising: placing a substrate with a dielectric film on a substrate support in a chamber; and etching the dielectric film with plasm generated from a reaction gas containing an HF gas and at least one C_(x)H_(y)F_(z) gas selected from the group consisting of a C₄H₂F₆ gas, a C₄H₂F₈ gas, a C₃H₂F₄ gas, and a C₃H₂F₆ gas, wherein the etching includes setting a temperature of the substrate support to be 0° C. or lower and setting a flow rate the HF gas to be greater than a flow rate of the C_(x)H_(y)F_(z) gas.
 2. The substrate processing method according to claim 1, wherein the flow rate of the C_(x)H_(y)F_(z) gas is less than or equal to 20% by volume of a total flow rate of the reaction gas.
 3. The substrate processing method according to claim 1, wherein the flow rate of the HF gas is greater than or equal to 70% by volume of a total flow rate of the reaction gas.
 4. The substrate processing method according to claim 1, wherein the reaction gas further contains a halogen-containing gas.
 5. The substrate processing method according to claim 4, wherein the halogen-containing gas is at least one gas selected from the group consisting of a chlorine-containing gas, a bromine-containing gas, and an iodine-containing gas.
 6. The substrate processing method according to claim 4, wherein the halogen-containing gas is at least one gas selected from the group consisting of Cl₂, SiCl₂, SiCl₄, CCl₄, SiH₂Cl₂, Si₂Cl₆, CHCl₃, SO₂Cl₂, BCl₃, PCl₃, PCl₅, POCl₃, Br₂, HBr, CBr₂F₂, C₂F₅Br, PBr₃, PBr₅, POBr₃, BBr₃, HI, CF₃I, C₂F₅I, C₃F₇I, IF₅, IF₇, I₂, and P₁₃.
 7. The substrate processing method according to claim 1, wherein the reaction gas further contains a phosphorus-containing gas.
 8. The substrate processing method according to claim 1, wherein the reaction gas further contains an oxygen-containing gas.
 9. The substrate processing method according to claim 1, wherein the reaction gas further contains at least one gas selected from the group consisting of a boron-containing gas and a sulfur-containing gas.
 10. The substrate processing method according to claim 1, wherein the plasma is generated from a process gas containing the reaction gas and an inert gas.
 11. The substrate processing method according to claim 1, wherein the dielectric film is a silicon-containing film.
 12. The substrate processing method according to claim 11, wherein the silicon-containing film includes at least one film selected from the group consisting of a silicon oxide film, a silicon nitride film, and a polysilicon film.
 13. The substrate processing method according to claim 1, wherein the substrate includes a mask including an organic film defining at least one opening on the dielectric film or a metal-containing film defining at least one opening on the dielectric film.
 14. The substrate processing method according to claim 1, wherein the etching includes applying an electrical bias to the substrate support, a period during which the electrical bias is applied to the substrate support includes a first period and a second period that alternates with the first period, and a level of the electrical bias in the first period is zero or at a first level, and a level of the electrical bias in the second period is at a second level higher than the first level.
 15. The substrate processing method according to claim 14, wherein the etching includes providing radio-frequency power for generating the plasma to the substrate support or to an upper electrode facing the substrate support, a period during which the radio-frequency power is provided includes a third period and a fourth period that alternates with the third period, a level of the radio-frequency power in the third period is zero or at a third level, and a level of the radio-frequency power in the fourth period is at a fourth level higher than the third level, and the second period and the fourth period at least partially overlap.
 16. The substrate processing method according to claim 14, wherein the electrical bias is a pulsed voltage.
 17. The substrate processing method according to claim 1, wherein the etching includes providing a direct-current voltage or low-frequency power to an upper electrode facing the substrate support.
 18. The substrate processing method according to claim 1, wherein the etching includes a first process of setting a pressure inside the chamber to a first pressure, applying a first electrical bias to the substrate support, and etching the dielectric film, and a second process of setting the pressure inside the chamber to a second pressure, applying a second electrical bias to the substrate support, and etching the dielectric film, and the first pressure differs from the second pressure or the first electrical bias differs from the second electrical bias, or the first pressure differs from the second pressure and the first electrical bias differs from the second electrical bias.
 19. The substrate processing method according to claim 18, wherein the first pressure is higher than the second pressure.
 20. The substrate processing method according to claim 18, wherein an absolute value of the first electrical bias is greater than an absolute value of the second electrical bias.
 21. The substrate processing method according to claim 18, wherein the first process and the second process are repeated alternately.
 22. A substrate processing method, comprising: placing a substrate with a silicon-containing film including a silicon oxide film on a substrate support in a chamber; and etching the silicon-containing film with plasm generated from a reaction gas containing a fluorine-containing gas and a C_(x)H_(y)F_(z) gas being a gas different from the fluorine-containing gas, where x is an integer greater than or equal to 2, and y and z are integers greater than or equal to 1, wherein the etching includes setting a temperature of the substrate support to be 0° C. or lower and setting a flow rate of the C_(x)H_(y)F_(z) gas to be less than or equal to 20% by volume of a total flow rate of the reaction gas.
 23. The substrate processing method according to claim 22, wherein the fluorine-containing gas is a gas to produce an HF species in the chamber.
 24. The substrate processing method according to claim 22, wherein the C_(x)H_(y)F_(z) gas includes one or more CF₃ groups.
 25. The substrate processing method according to claim 24, wherein the C_(x)H_(y)F_(z) gas contains at least one gas selected from the group consisting of a C₃H₂F₄ gas, a C₃H₂F₆ gas, a C₄H₂F₆ gas, a C₄H₂F₈ gas, and a C₅H₂F₆ gas.
 26. The substrate processing method according to claim 22, wherein a flow rate of the fluorine-containing gas is highest among flow rates of all gases in the reaction gas.
 27. A substrate processing method, comprising: placing a substrate with a silicon-containing film including a silicon oxide film on a substrate support in a chamber; generating plasma in the chamber; and etching the silicon-containing film using an HF species and a C_(x)H_(y)F_(z) species in the plasma, where x is an integer greater than or equal to 2, and y and z are integers greater than or equal to 1, wherein the plasma includes a greatest amount of the HF species among all species in the plasma.
 28. A substrate processing apparatus, comprising: a chamber; a substrate support in the chamber, a temperature of the substrate support being adjustable; a plasma generator to provide electric power to generate plasma in the chamber; and a controller, wherein the controller performs a control operation including introducing, using the electric power provided from the plasm generator, a reaction gas containing an HF gas and at least one C_(x)H_(y)F_(z) gas selected from the group consisting of a C₄H₂F₆ gas, a C₄H₂F₈ gas, a C₃H₂F₄ gas, and a C₃H₂F₆ gas into the chamber to generate the plasma to etch a dielectric film in a substrate supported on the substrate support, and the control operation includes setting a temperature of the substrate support to be 0° C. or lower and setting a flow rate of the HF gas to be greater than a flow rate of the C_(x)H_(y)F_(z) gas. 